1. Field of the Invention
The present invention relates to a refrigerant transportation hose such as an air-conditioner hose and specifically to a refrigerant transportation hose, for transporting refrigerant (gas or liquid) such as carbon dioxide (CO2), chlorofluorocarbon (Freon, trademark of Du Pont de Nemours and Company), chlorofluorocarbon's (CFC's) substitute and propane, that is mounted in an engine compartment or the like of an automobile.
2. Description of the Related Art
Generally, a rubber hose is used for a refrigerant transportation hose that is mounted in an engine compartment of an automobile in terms of assembility, flexibility, capability of controlling vibration transmission and the like. For example, proposed is a hose having a structure of a tubular inner rubber layer in which refrigerant is circulated, a reinforcing layer formed on an outer peripheral surface of the tubular inner rubber layer and an outer rubber layer formed on an outer peripheral surface of the reinforcing layer (for example, see Japanese Unexamined Patent Publication No. 07-068659).
To suppress permeation of refrigerant such as chlorofluorocarbon (Freon) or CFC's substitute (such as R134a) or enhance a barrier property against refrigerant, proposed is a hose of which an innermost layer is formed by polyamide resin (PA) or a hose containing metallic foil or metallized laminate (for example, see Japanese Unexamined Patent Publication No. 2001-241572).
Since chlorofluorocarbon (Freon) conventionally used as refrigerant for an air-conditioner of an automobile or the like leads to destruction of an ozone layer in the atmosphere, the use thereof has been already prohibited. Further, restriction of emission reduction is now applying to CFC's substitute such as R134a. Under such circumstances, it is thought that carbon dioxide (CO2) refrigerant (liquid or gas), which may impart less adverse affects on the environment, will be mainly used as refrigerant for air-conditioners in the future.
However, carbon dioxide refrigerant has high permeability as compared with conventional refrigerant such as R134a and thus penetrates even a barrier layer based on polyamide 6 (PA6) effective for conventional refrigerant. For this reason, if a conventional refrigerant transportation hose is used for transporting carbon dioxide refrigerant, cooling capacity is deteriorated.
On the other hand, the hose containing a laminate such as metallic foil has a defect that the laminate tends to peel and thus a low-permeation property of refrigerant gas tends to deteriorate. Further, as a hose excellent in a low-permeation property, for example, proposed is a hose containing an ethylene vinyl alcohol copolymer (EVOH) layer, which, however, tends to be inferior in flexibility.